javax.sound.sampled
Interface TargetDataLine

A target data line is a type of DataLine from which
audio data can be read. The most common example is a data line that gets
its data from an audio capture device. (The device is implemented as a
mixer that writes to the target data line.)

Note that the naming convention for this interface reflects the relationship
between the line and its mixer. From the perspective of an application,
a target data line may act as a source for audio data.

The target data line can be obtained from a mixer by invoking the
getLine
method of Mixer with an appropriate
DataLine.Info object.

The TargetDataLine interface provides a method for reading the
captured data from the target data line's buffer.Applications
that record audio should read data from the target data line quickly enough
to keep the buffer from overflowing, which could cause discontinuities in
the captured data that are perceived as clicks. Applications can use the
available method defined in the
DataLine interface to determine the amount of data currently
queued in the data line's buffer. If the buffer does overflow,
the oldest queued data is discarded and replaced by new data.

open

Opens the line with the specified format and requested buffer size,
causing the line to acquire any required system resources and become
operational.

The buffer size is specified in bytes, but must represent an integral
number of sample frames. Invoking this method with a requested buffer
size that does not meet this requirement may result in an
IllegalArgumentException. The actual buffer size for the open line may
differ from the requested buffer size. The value actually set may be
queried by subsequently calling DataLine.getBufferSize()

If this operation succeeds, the line is marked as open, and an
OPEN event is dispatched to the
line's listeners.

Invoking this method on a line that is already open is illegal
and may result in an IllegalStateException.

Some lines, once closed, cannot be reopened. Attempts
to reopen such a line will always result in a
LineUnavailableException.

open

Opens the line with the specified format, causing the line to acquire any
required system resources and become operational.

The implementation chooses a buffer size, which is measured in bytes but
which encompasses an integral number of sample frames. The buffer size
that the system has chosen may be queried by subsequently calling DataLine.getBufferSize()

If this operation succeeds, the line is marked as open, and an
OPEN event is dispatched to the
line's listeners.

Invoking this method on a line that is already open is illegal
and may result in an IllegalStateException.

Some lines, once closed, cannot be reopened. Attempts
to reopen such a line will always result in a
LineUnavailableException.

read

int read(byte[] b,
int off,
int len)

Reads audio data from the data line's input buffer. The requested
number of bytes is read into the specified array, starting at
the specified offset into the array in bytes. This method blocks until
the requested amount of data has been read. However, if the data line
is closed, stopped, drained, or flushed before the requested amount has
been read, the method no longer blocks, but returns the number of bytes
read thus far.

The number of bytes that can be read without blocking can be ascertained
using the available method of the
DataLine interface. (While it is guaranteed that
this number of bytes can be read without blocking, there is no guarantee
that attempts to read additional data will block.)

The number of bytes to be read must represent an integral number of
sample frames, such that:

[ bytes read ] % [frame size in bytes ] == 0

The return value will always meet this requirement. A request to read a
number of bytes representing a non-integral number of sample frames cannot
be fulfilled and may result in an IllegalArgumentException.

Parameters:

b - a byte array that will contain the requested input data when
this method returns

off - the offset from the beginning of the array, in bytes

len - the requested number of bytes to read

Returns:

the number of bytes actually read

Throws:

IllegalArgumentException - if the requested number of bytes does
not represent an integral number of sample frames.
or if len is negative.